dp bio topic 3-1 genes
TRANSCRIPT
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Topic 3.1 GenesIB Biology
R. Price
v. 1 2015
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Allott 141
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#1: A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic
Genes• Made of DNA• Influences specific characteristic
(height, eye color, blood type)• Can be passed on to offspring
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Allott 142
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#2: A gene occupies a specific position on one type of chromosome
Chromosomes• Genes are linked in groups• Each group is a type of
chromosome• Most plants & animals have two
copies of each chromosome• Locus = specific place on the
chromosome where a specific gene is located
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Allott 143
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#3: The various specific forms of a gene are alleles
Alleles• Alternative forms of the same
gene• Cause for wide variation in
characteristics such as eye color, hair color, fur color, blood type• Only one allele per chromosome• Have a pair of each type of
chromosome, so may have two different alleles
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Allott 144
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Allott 145
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#4: Alleles differ from each other by one or a few bases only
• Genes can be hundreds or thousands of bases long• Alleles are different by only one
or a few bases• Positions in a gene where more
than one base may be present are called single nucleotide polymorphisms (SNPs)
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Allott 146
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#5: New alleles are formed by mutation
Base Substitution• One base in sequence of a
gene is replaced by a different base• Most mutations are neutral
or harmful• Body cell mutation gone
when individual dies• Sperm or egg mutation may
be passed onto offspring
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#6: The genome is the whole of the genetic information of an organism
Entire base sequence of each of the DNA molecules• In animals• DNA in chromosomes• DNA in mitochondria
• In plants • DNA in chromosomes,
mitochondria, & chloroplasts
• In prokaryotes• DNA in circular chromosome +
plastids
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#7: The entire base sequence of human genes was sequenced in the Human Genome Project
Human Genome Project• 1990-2003• One set of chromosomes• Not total understanding of
genetics, but great data• Using this data
• can predict which base sequences are protein coding genes
• Found satellite DNA• “junk” DNA affects gene expression
First printout of Human Genome Project
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Allott 148
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Sources
Content Allott, Andrew, and David Mindorff. Biology: Course Companion. 2014 ed. Oxford: Oxford UP, 2014. Print. Oxford IB Diploma Programme.
Walpole, Brenda. Biology for the IB Diploma. 2nd ed. Cambridge: Cambridge UP, 2014. Print.
ImagesUnless otherwise noted, images are obtained from Pixabay (www.pixabay.com) and used under the CC0 Public Domain license.